Valve regulating means disposed between HV switching apparatus and over voltage arresting mechanism maintaining pressure differential therebetween

ABSTRACT

An improved voltage overload arresting apparatus for a highvoltage switching system in which the housings of the arresting apparatus and the switching system are coupled by a reduction valve which maintains the pressure of a dense gaseous insulating medium in the arresting apparatus housing at a constant pressure which is less than the gas pressure in the switching system housing.

Unlted States Patent 11 1 1111 3,881,138 Luxa et al. 1 1 Apr. 29, 1975VALVE REGULATING MEANS DISPOSED 3.280.376 I 10/1966 Person 317/70 xBETWEEN Hv SWITCHING APPARATUS 3.378.731 4/1968 Whitehead... 317/1033.566.062 2/1971 Meier et 200/145 R X AND OVER VOLTAGE ARRESTING3.566.183 2/1971 Olsen et 111.... 317/70 x MECHANISM MAINTAININGPRESSURE 3.622.725 11/1971 McConnc|l.... 200/148 B x DIFFERENTIALTHEREBETWEEN 3.733.521 5/1973 Kalb 317/70 3.743.804 7/1973 Frowcin317/103 X I75] "Vemors: Werner Jaksz" both 3.777.218 12/1973 Kesslcr317/71 x of Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft,Munich,

Germany Primary E.\'am1'nerlames R. Scott Attorney, Agent, or FirmKenyon& Kenyon Reilly [22] Filed. July 2, 1973 c & Chapin [21] Appl. No.:375,518

[30] Foreign Application Priority Data July 14, 1972 Germany 2235514[57] ABSTRACT [52] U.S. Cl. 317/59; 200/148 B; 200/148 E; An improvedvoltage Overload arresting apparatus for 317/71; 317/103 a high-voltageswitching system in which the housings [51] Int. Cl H02h 1/00; H01h33/80 of the ing pp ratus nd he switching system [58] Field of Search317/69, 70, 103, 59, 60, are coupled by a reduction valve whichmaintains the 317/71; 200/145 R, 146 A, 146 AA 148 B, pressure of adense gaseous insulating medium in the 148 E 148 R arresting apparatushousing at a constant pressure which is less than the gas pressure inthe switching sys- [56] References Cited tem housing.

UNITED STATES PATENTS 3.072.828 1/1963 Goffaux 317/70 X 10 Claims, 4Drawing Figures PATENTEflAFazsiazs 3,881,138

SHEET 20F 2 Fig. 2

FILTEEI Z4 III- Fig.3

FILTE Fly SPARK GAP l VALVE REGULATING MEANS DISPOSED BETWEEN HVSWITCHING APPARATUS AND OVER VOLTAGE ARRESTING MECHANISM MAINTAININGPRESSURE DIFFERENTIAL THEREBETWEEN BACKGROUND OF THE INVENTION 1. Fieldof the Invention The invention relates to high-voltage switchingsystems, and in particular, to a high-voltage switching system of thetype utilizing a dense, gaseous insulating medium which includes animproved voltage overload arresting apparatus.

2. Description of the Prior Art German Auslegeschrift Pat. No. 1,241,514discloses a high-voltage switching system which is encapsulated in ametal housing and includes a spark gap. The housing is filled with adense, insulating gas, such as. for example. sulfur hexafluoride, inwhich gaseous insulating medium the spark gap operates. Improvedswitching systems of the type described above generally include voltageoverload arresting apparatus which comprise both a spark gap and anarrangement of voltage dependent resistors which limit current surges.It is known, as taught by US Pat. No. 2,757,26l, that improvedperformance of a voltage overload arresting apparatus can be obtained byfilling the housing thereof with sulfur hexafluoride. The correlationbetween the pressure of the gas in the voltage overload arrestingapparatus housing, and the ratio of the breakdown voltage to thequenching voltage, especially when sulfur hexafluoride is usedas theinsulating medium. has. however, not been appreciated by the prior art.

SUMMARY OF THE INVENTION It is therefore an object of the invention toprovide an improved high-voltage switching system voltage overloadarresting apparatus in which the pressure of a gaseous insulating mediumin the arresting apparatus housing is controlled with respect to thepressure of the same gaseous insulating medium in the switching systemhousing.

Accordingly, the invention provides, in a highvoltage switching systemof the type described above, regulating means, coupled to the housing ofthe switching apparatus at one end, and to the housing of the voltageoverload arresting apparatus at the other end thereof, for regulatingthe pressure within the housing of the arresting apparatus so as tomaintain the pressure of a gaseous insulating medium therein at aconstant pressure which is less than the pressure of the same gaseousinsulating medium in the housing of the switching system. In oneembodiment of the invention, the regulating means comprises a reductionvalve coupled to the switching system housing and the voltage overloadarresting apparatus housing. A filtering means and pump may also becoupled to a line connecting the housings, for purifying the gaseousinsulating medium flowing from the switching system housing to thevoltage overload arresting apparatus housing. In another embodiment ofthe invention, the arresting apparatus housing includes a separatesealed chamber fora spark gap, and another sealed chamber for a voltagedependent resistor arrangement thereof. The chambers in which theresistors are disposed may also be separately coupled to the housing ofthe switching system by means of a suitable connecting line. andpreferably includes a check valve which prevents contaminated gas fromflowing into the switching system housing. In still another embodimentof the invention, the spark gap of the arresting apparatus is dividedinto a pair of spark gaps. one of which comprises an ignition spark gap,disposed in separate sealed chambers. A contact breaker device iscoupled to the ignition spark gap for triggering the apparatus when avoltage overload occurs.

DESCRIPTION OF THE DRAWINGS In the drawings, wherein similar referencenumerals denote similar elements throughout the several views thereof:

FIG. 1 is a schematic side view, partially in section, of a high-voltageswitching system, including an improved voltage overload arrestingapparatus constructed according to the invention;

FIG. 2 is a schematic illustration of one embodiment of an improvedvoltage overload arresting apparatus constructed according to theinvention;

FIG. 3 is a schematic illustration of another embodiment of an improvedarresting apparatus constructed according to the invention, wherein thearresting apparatus housing is divided into separate chambers forcontaining the voltage dependent resistors and the spark gap of thearresting apparatus; and

FIG. 4 is a schematic illustration of still another embodiment of animproved arresting apparatus constructed according to the invention,which utilizes an ignition spark gap as part of the arresting apparatus.

DETAILED DESCRIPTION Referring now to the drawings, FIG. 1 illustrates ahigh-voltage switching system having a metal housing and a voltageoverload arresting apparatus coupled thereto. The system includes athree-phase dual bus bar system (which may be, for example, I I0 kV)including bus bars 1 and 2 and circuit breakers 3 and 4 coupled thereto.The circuit breakers are coupled to each other by a feed line 5.Terminal 7, which may be connected to an electrical cable distributionline, is coupled by feed line 6 to the circuit breakers and bus bars.Conductor 8 is coupled to the feed line 5 and connects terminal 7 tocircuit breakers 3 and 4. A voltage overload arresting apparatus 9 isdisposed beneath the housing 10 of the high-voltage switching system andis coupled thereto by a pressure resistant line 13. The arrestingapparatus is also electrically connected to conductor 8 in housing 10 byanother conductor.

Interior space 11 of switching system housing 10, and interior space 14of arresting apparatus housing 12, are also coupled to each other bymeans of a line 15. Regulating means 16 is coupled to the line andregulates the pressure of the gaseous insulating medium in housing 12 ofthe arresting apparatus relative to the pressure in housing 10 of theswitching system. The regulating means may, for example, comprise areduction valve which may simultaneously prevent backflow of gas fromhousing 12 to housing 10 when an overload occurs and the pressure inhousing 12 rapidly increases.

One embodiment of the improved arresting apparatus is illustrated inFIG. 2. In this embodiment, housing 10 is coupled to housing 12 by meansof a line 23, and a filtering means shown as filter 24, is disposedbetween the housings and coupled to the line. The gaseous insulatingmedium flows through line 23 from housing 10 to housing 12 throughfilter 24 which, in combination with a pump 21, ensures that the gas ispurified before it is admitted to the arresting apparatus housing: Thisfiltering process carried out by pump 21 and filter 24 ensures that thebreakdown voltage of the spark gap of the arresting apparatus ismaintained at a constant voltage level. Reduction valve 22 operates tomaintain the pressure inthe arresting apparatus housing 12 at a constantpressure which is slightly below that of the pressure in the switchingsystem housing 10. Pump 21 and valve 22 are coupled to housing by line20.

Inthe embodiment of the invention illustrated in FIG. 3, arrestingapparatus includes a separate chamber 31 in which spark gap 32 isdisposed, and an additional chamber 33 in which the voltage dependentresistors 34 are disposed. The spark gap utilized throughout the variousembodiments of the invention comprises a known series connection ofindividual spark gaps, and the voltage dependent resistors are formed'bya column of individual resistor elements. The separation of thehousing into sealed chambers in this embodiment prevents decompositionproducts,

which are formed when a voltage overload occurs by the burning of theinsulating gas, from flowing into the "switching system housing Y10 andcontaminating the gaseous atmosphere therein. As in the previouslydescribed embodiment of the invention, a pump and a reduction valve arecoupled by means of line 35 to the arresting apparatushousing and theswitching system housing. ln thisembodiment, chamber 31 is sealed, and

the pressure is regulated as previously described by the reductionvalve. A filtering means is also coupled by a line 36 to the switchingsystem housing and arresting apparatus chamber 31. Chamber 33, in whichthe voltage dependent resistors 34 are disposed, is sealed and is-filledwith the same gas utilized as a gaseous insulating medium in housing 10,namely, sulfur hexafluoride,

. at a pressure which is higher than the pressure in chamber 31. Thedielectric strength of the arresting apparatus is thus improved,especially under large pulse currents, since the insulating capacity ofthe gas increases as the gas pressure increases. Flashover is thusprevented. Chamber 33 is coupled by means of line 37 to housing 10 ofthe switching system, which line includes a check valve 38 coupledthereto. The line equalizes the pressure in chamber 33 and in housing10, and the check valve prevents contaminated gas from being forced intohousing 10 upon the occurence ofa voltage overload.

ln the embodiment of the invention illustrated in FIG. 4, voltagearresting apparatus 40 includes a separately sealed chamber 41 for thevoltage dependent resistors of the arresting apparatus. The spark gap ofthe gap in a known manner. Chamber 41, in which the voltage dependentresistors are disposed, may be connected to the interior of housing 10of the switching system as described in the previous embodiments of theinvention. Chamber 45, in which spark gap 43 is disposed, contains agaseous insulating medium which is [different than that used as aninsulating medium in switching apparatus housing 10, such as, forexample,

nitrogen. The breakdown voltage of spark. gapi, 43 is thus lower thanthe breakdown voltage of sparkgfap 42,

and, as a result, automatic triggering of'the spark gap is achieved.Controlled firing of the voltage'arresting apparatus, and precisecontrol of the voltage breakdown levels, are obtained. 1

It should be noted that the several illustrated divisions of the voltagearresting apparatus housing into separate chambers can be combined with'feature's of the other embodiments of the inventionflt isirnportant onlythat the main portion of the spark gap of the apparatus be surroundedwith the insulating gaseous medium utilized in the high-voltageswitching system housing at a constant and at a reduced pressure, sothat the desired breakdown voltage/quenching"voltage ratio is obtained.

While there have been described herein what are I considered to bepreferred embodiments of the invention, it will be clear to thosepersons skilled in the art that many changes and modifications may bemade thereunto without departing from the invention, and it is thereforeintended in the appended claims to include all such changes andmodifications as fall within the true spirit and scope thereof.

What is claimed is:

1. In a high voltage switching system, of the type including a switchingsystem housing in which a dense gaseous insulating medium is disposedunder pressure, and a voltage overload arresting apparatus including ahousing, having at least one first sealed chamber coupled to theswitching system housing,also containing said dense gaseous insulatingmedium, and at least one spark gap, and voltage dependent resistancemeans, disposed in said arresting apparatus housing, the improvementcomprising regulating means including valve means, coupled to theswitching system housing and to said arresting apparatus housing, formaintaining the pressure of said gaseous insulating medium in saidchamber at a constant pressure which is less than the pressure of saidgaseous insulating medium in the switching system housing.

2. The apparatus as recited in claim 1, wherein said regulating meansvalve means comprises a reduction valve coupled to the switching systemhousing and said chamber of said arresting apparatus housing.

3. The apparatus as recited in claim 2, wherein said regulating meanscomprises said reduction valve in combination with a check valve forpreventing the flow of said gaseous insulating medium from saidarresting I apparatus housing to the switching system housing.

4. The apparatus as recited in claim 2, further comprising filteringmeans, and a pump, coupled to the switching system and said arrestingapparatus housings, for purifying gas flowing from the switching'systemhousing into said arresting apparatus housing.

5. The apparatus as recited in claim 4, wherein said arresting apparatushousing further comprises a second sealed chamber in which said voltagedependent resistance means is disposed, said spark gap being disposed insaid first housing chamber, and said pump, valve, and filtering meansbeing coupled to said first chamber.

6. The apparatus as recited in claims, wherein said second housingchamberis coupled t'othe" switching system housing by aline for fillingsaid sec o nd'c har nber with the gaseous insulating medium in theswitching system housing to "a pressure equal to 'the pressure in theswitching system housing. J

7. The apparatus as recited in claim 6, further comprising valve means,coupled to said line, for preventing flow of the gaseous insulatingmedium from said second chamber to the switching system housing.

8. The apparatus as recited in claim 1, wherein said arresting apparatushousing includes a second sealed chamber, first and second spark gapsbeing disposed in said first and second chambers. respectively. and athird sealed chamber in which said voltage dependent resistance means isdisposed, and further comprising a line coupled to the switching systemhousing and one of said first and second chambers, filtering meanscoupled to said line for purifying said gaseous insulating mediumflowing through said line into said arresting ap paratus housing, saidother of said first and second chambers containing a gaseous insulatingmedium which is different than the gaseous insulating medium in theswitching system housing.

9. The apparatus as recited in claim 8, wherein said spark gap disposedin said other of said first and second chambers comprises an ignitionspark gap.

10. The apparatus as recited in claim 9, further comprising contactbreaker means, coupled to said ignition spark gap, for triggering saidspark gap upon the occurrence of a voltage overload.

1. In a high voltage switching system, of the type including a switchingsystem housing in which a dense gaseous insulating medium is disposedunder pressure, and a voltage overload arresting apparatus including ahousing, having at least one first sealed chamber coupled to theswitching system housing, also containing said dense gaseous insulatingmedium, and at least one spark gap, and voltage dependent resistancemeans, disposed in said arresting apparatus housing, the improvementcomprising regulating means including valve means, coupled to theswitching system housing and to said arresting apparatus housing, formaintaining the pressure of said gaseous insulating medium in saidchamber at a constant pressure which is less than the pressure of saidgaseous insulating medium in the switching system housing.
 2. Theapparatus as recited in claim 1, wherein said regulating means valvemeans comprises a reduction valve coupled to the switching systemhousing and said chamber of said arresting apparatus housing.
 3. Theapparatus as recited in claim 2, wherein said regulating means comprisessaid reduction valve in combination with a check valve for preventingthe flow of said gaseous insulating medium from said arresting apparatushousing to the switching system housing.
 4. The apparatus as recited inclaim 2, further comprising filtering means, and a pump, coupled to theswitching system and said arresting apparatus housings, for purifyinggas flowing from the switching system housing into said arrestingapparatus housing.
 5. The apparatus as recited in claim 4, wherein saidarresting apparatus housing further comprises a second sealed chamber inwhich said voltage dependent resistance means is disposed, said sparkgap being disposed in said first housing chamber, and said pump, valve,and filtering means being coupled to said first chamber.
 6. Theapparatus as recited in claim 5, wherein said second housing chamber iscoupled to the switching system housing by a line for filling saidsecond chamber with the gaseous insulating medium in the switchingsystem housing to a pressure equal to the pressure in the switchingsystem housing.
 7. The apparatus as recited in claim 6, furthercomprising valve means, coupled to said line, for preventing flow of thegaseous insulating medium from said second chamber to the switchingsystem housing.
 8. The apparatus as recited in claim 1, wherein saidarresting apparatus housing includes a second sealed chamber, first andsecond spark gaps being disposed in said first and second chambers,respectively, and a third sealed chamber in which said voltage dependentresistance means is disposed, and further comprising a line coupled tothe switching system housing and one of said first and second chambers,filtering means coupled to said line for purifying said gaseousinsulating medium flowing through said line into said arrestingapparatus housing, said other of said first and second chamberscontaining a gaseous insulating medium which is different than thegaseous insulating medium in the switching system housing.
 9. Theapparatus as recited in claim 8, wherein said spark gap disposed in saidother of said first and second chambers comprises an ignition spark gap.10. The apparatus as recited in claim 9, further comprising contactbreaker means, coupled to said ignition spark gap, for triggering saidspark gap upon the occurrence of a voltage overload.